Atomic-scale Characterization of Surface and Interface Dynamics in Novel Materials: Cr2Ge2Te6, NbSe2, and Strontium Barium Niobate




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Transition metal dichalcogenides (TMDs) and transition metal trichalcogenides (TMT) are promising layered materials for novel electronic and optoelectronic device applications due to their fascinating electronic, optical, magnetic, and chemical properties with two dimensional (2D) atomic limits. However, their thermal stability and thermally induced defects, which are crucial for reliable operation of the devices, remain an area for further investigations. The electro-optic (EO) materials with high Pockels coefficient are also an intriguing research field for fast, small, and low power consumption electro-optical devices. Integrating the EO materials on the current silicon technologies is challenging due to demands for high crystal quality and sensitivity to orientation but highly desirable to expand their application field with compact design and low power consumption. This dissertation focuses on the thermal stability and thermal evolution studies of 𝑁𝑏𝑆𝑒2(TMD) and 𝐶𝑟2𝐺𝑒2𝑇𝑒6 (TMT) at the surface and material interface by employing in-situ scanning transmission electron microscopy (STEM) to probe the dynamics of thermal evolution and defects. The interface and surface of molecular beam epitaxial (MBE) grown strontium barium niobate on silicon with strontium titanate buffer layer is also investigated using STEM to understand the nature and growth mechanism.



Engineering, Materials Science